1. Field of the Invention
This invention relates to a ferroelectric element and method for manufacturing the same and, more particularly, to a ferroelectric element having a hydrogen blocking film formed directly on a surface of the upper electrode thereof and a method for manufacturing the same.
2. Description of Related Art
There is, as a ferroelectric element, a ferroelectric capacitor structured by a ferroelectric film, such as of PZT or SBT, sandwiched between the upper and lower electrodes of Pt or the like. The ferroelectric capacitor, for holding data in a non-volatile fashion by the utilization of a spontaneous polarization characteristic of the ferroelectric film, is utilized for a non-volatile semiconductor memory (FeRAM, Ferroelectric Random Access Memory).
The ferroelectric capacitor used for a semiconductor memory or the like has a structure described, for example, in Patent Documents 1 and 2. In the ferroelectric capacitor described in Patent Documents 1 and 2, a lower electrode, a ferroelectric film and an upper electrode are layered and patterned in the order, and then these are covered by a reaction preventing film (hydrogen blocking film) and an oxide film (interlayer insulation film) in that order. Then, a contact hole (opening) is formed in the hydrogen blocking film and oxide film, to expose the upper electrode. Through the opening, a metal interconnect layer is (interconnect film) connected to the upper electrode.
[Patent document 1] JP-A-2002-305288 (page 3, FIG. 1)
[Patent document 2] JP-A-11-121704 (pages 1–8, FIGS. 1–6)
In the ferroelectric capacitor described in Patent documents 1 and 2, the opening having a constant diameter is formed through the hydrogen blocking film and oxide film covering the lower electrode, ferroelectric film and upper electrode, thereby forming an interconnect film in the opening. However, because the hydrogen blocking film is removed at the opening, hydrogen possibly enters at the opening into the ferroelectric film through the upper electrode thereby deteriorating the ferroelectric film, resulting in a fear causing deterioration in the feroelectric film. Meanwhile, in order to prevent the intrusion of hydrogen, in case the opening portion is made smaller while maintaining the opening at the constant diameter, the opening has an increased aspect ratio. This worsens the coverage of the interconnect film connected to the upper electrode through the opening, which possibly causes a fear of lowered reliability of the interconnect film.
It is an object of the present invention to prevent, in a ferroelectric element, the ferroelectric film from deteriorating and the interconnect film from lowering in reliability.